Cigarette filter

ABSTRACT

A cigarette filter that includes a multiple section filter which reduces the level of predetermined smoke constituents. The filter consists of a fibrous filter plug located at the mouth-end of the cigarette, a section containing a selective adsorbent material, and a section containing a general adsorbent material. The selective adsorbent material, such as a phenol-formaldehyde resin matrix surface-functionalized with mainly primary and secondary amine functional groups, removes specific smoke constituents from the tobacco smoke. The general adsorbent material, such as activated charcoal, is preferably capable of adsorbing a range of chemical compounds without a high degree of specificity. Structurally, the fibrous filter plug, the selective adsorbent section, and the general adsorbent section are co-axially aligned in tandem.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

[0001] This application claims priority from U.S. Provisional Application Ser. No. 60/309,388, filed Aug. 1, 2001, which application is incorporated herein by reference in its entirety.

BACKGROUND

[0002] The present invention relates to a cigarette filter that includes a smoke constituent adsorbent which, when combined with a carbon-based filtering material, demonstrates synergistic reductions in smoke vapor constituents.

[0003] Cigarettes include tobacco rods or columns which, when burned, produce a particulate and a vapor phase. About 70 years ago, filters began to be attached to an end of the tobacco column. Among other things, the filter removed various smoke components. Filters made from filamentary or fibrous material, such as cellulose acetate tow or paper, remove the particulate phase of tobacco smoke by mechanical means. However, the fibrous materials are not effective at removing volatile constituents, such as aldehydes, hydrogen cyanide and sulfides, which are found in the vapor phase. Typically, an adsorbent or absorbent is combined with the fibrous material to improve removal of the vapor phase components. For example, cigarette filters have included activated carbon, porous minerals such as meerschaum, silica gel, cation-exchange resins and anion-exchange resins.

[0004] Charcoal has a high specific surface area and is a relatively strong adsorbent for vapor-phase constituents of tobacco smoke. When coated with a mixture of metallic oxides, charcoal is particularly effective in removing acidic gases. Meerschaum has a large adsorption area with a strong adsorption affinity for charged species, but a considerably low adsorption affinity for non-polar species. Silica gels are generally regarded as weakly retentive adsorbents for vapor-phase constituents of tobacco smoke. Although silica gel readily adsorbs aldehydes and hydrogen cyanide, the constituents also readily desorb from the silica gel. Cation exchange resins have been proposed for nicotine removal. Anion exchange resins have been proposed for the removal of smoke acids, but strongly basic anion exchangers have no effect on smoke vapor phase aldehydes. Weakly basic anion-exchange resins of porous structure are suitable for the removal of smoke acids and aldehydes, but their efficiency diminishes during smoking, as does that of carbon and porous minerals.

[0005] Two or more adsorbents can be used in combination in cigarette filters. For example, U.S. Pat. No. 2,815,760 describes the use of an ion exchange material with materials which “chemically react with the harmful, nonalkaline and nonacid components of the smoke to form non-volatile compounds, thus retaining the latter to the filter.” However, the aforesaid additives have not yielded satisfactory selective removal of such smoke phase components, as smoke aldehydes, particularly acetaldehyde and acrolein. U.S. Pat. No. 4,300,577 describes the use of a weakly retentive absorbent for vapor-phase constituents intermingled with a second component having mainly primary amino functional groups for the removal of vapor-phase constituents, including aldehydes and hydrogen cyanide from tobacco smoke. However, the filter of the '577 patent has not been shown to demonstrate adequate consumer acceptance or commercial viability.

SUMMARY

[0006] The present invention relates to a cigarette filter that includes a multiple section filter which reduces the level of predetermined smoke constituents. The filter consists of a fibrous filter plug located at the mouth-end of the cigarette, a section containing a selective adsorbent material, and a section containing a general adsorbent material.

[0007] The filter plug can be any filter plug known in the art, such as cellulose acetate tow. The general adsorbent material is preferably selected from a group of relatively high surface area materials, such as activated charcoal, which are capable of adsorbing a range of chemical compounds without a high degree of specificity. The selective adsorbent material is chosen based on the specific smoke constituents targeted for removal. Preferably, the selective adsorbent material is selected from a group of surface functionalized resins, wherein each resin consists of an essentially inert carrier with a surface area of greater than about 35 m²/g. In an embodiment of the present invention, the selective adsorbent material has a phenol-formaldehyde resin matrix surface-functionalized with mainly primary and secondary amine functional groups.

[0008] Structurally, the selective adsorbent material may be adjacent to a tobacco rod and the general adsorbent material positioned between the selective adsorbent section and the filter plug. Alternatively, the general adsorbent material may be positioned adjacent to the tobacco rod and the selective adsorbent material between the general adsorbent section and the filter plug. Preliminary data indicates that the former orientation produces a synergistic effect in smoke constituent reductions relative to the latter orientation. Further, the selective adsorbent and general adsorbent may be interspersed in a traditional filter plug material, such as cellulose acetate, or the adsorbents may be packed as a bed or thin layer sections within filter plug material.

SUMMARY OF THE FIGURES

[0009]FIG. 1 is a perspective view of a prior art filter-tipped cigarette;

[0010]FIG. 2 is a perspective view of a filter for a cigarette made in accordance with the present invention wherein the adsorbents are dispersed throughout a filter plug material, and the general adsorbent section is positioned between the filter plug and the selective adsorbent section;

[0011]FIG. 3 is a perspective view of a filter for a cigarette made in accordance with the present invention wherein the adsorbents are dispersed throughout a filter plug material, and the selective adsorbent section is positioned between the filter plug and the general adsorbent section; and

[0012]FIG. 4 is a perspective view of a filter for a cigarette made in accordance with the present invention wherein the adsorbents are packed as beds within a segment of a filter plug material.

[0013]FIG. 5 is a cross-sectional view of an embodiment of the present invention with the filter plug disposed between the general adsorbent section and the selective adsorbent section;

[0014]FIG. 6 is a cross-sectional view of an embodiment of the present invention with the filter plug adjacent one end of a tobacco rod;

[0015]FIG. 7 is a cross-sectional view of an embodiment of the present invention with the adsorbents being sectionalized in a single length of fibrous filter material; and, FIG. 8 is a cross-sectional view of an embodiment of the present invention absent a filter plug section.

DETAILED DESCRIPTION

[0016] The cigarette filter of the present invention includes a multiple section filter which reduces the levels of predetermined smoke constituents. The filter consists of a fibrous filter plug located at the mouth-end of the cigarette, a section containing a selective adsorbent material, and a section containing a general adsorbent material.

[0017] As shown in FIG. 1 and as is known in the art, a typical filter-tipped cigarette 10 has a filter 30 attached to a tobacco rod 20. The tobacco rod 20 consists of a loose tobacco-containing mixture 22 wrapped in a cigarette paper 24, and the filter 30 includes a filter plug 32 wrapped in a plug wrap 34. A sheet of tipping paper 36 joins the filter 30 to the tobacco rod 20.

[0018] In the present invention, as shown in FIG. 2, a cigarette 110 has a multiple section filter 130 attached to the tobacco rod 20. The filter 130 includes a filter plug 132, a section containing a general adsorbent 134 and a section containing a selective adsorbent 136. The filter plug 132 is adjacent a first or mouth end 131 of the filter 130. The bed of the selective adsorbent 136 is adjacent a second or tobacco-rod end 137 of the filter 130. The bed of the general adsorbent 134 is positioned between the filter plug 132 and the selective adsorbent bed 136.

[0019] The filter plug 132 is made from a filamentary or fibrous material and provides a clean, neat appearance at the mouth end 131 of the cigarette. The filter plug 132 also retains a firmness at the mouth end 131 as the cigarette 110 is consumed. As is known in the art, the filter plug 132 can be made from a variety of materials, among the most common being cellulose, cellulose acetate tow, paper, cotton, polypropylene web, polypropylene tow, polyester web, polyester tow or combinations thereof. Optionally, a plasticizer may be included.

[0020] The general adsorbent section 134 includes a general adsorbent material 144 dispersed throughout a filter plug material 142, such as in a “dual-dalmatian” filter, known in the art. The general adsorbent material 144 is preferably selected from a group of relatively high surface area materials which are capable of adsorbing smoke constituents without a high degree of specificity. For example, the general adsorbent can be selected from activated charcoal, activated coconut carbon, activated coal-based carbon, a mineral-based charcoal made from semi-anthracite coal with a density about 50% greater than coconut-based charcoal (available from Calgon Carbon, Pittsburgh, Pa.), Ambersorb 572 or Ambersorb 563 (a carbonaceous resin derived from the pyrolysis of sulfonated styrene-divinylbenzene available from Rohm and Haas, 5000 Richmond Street, Philadelphia, Pa. 19137), other materials having similar particle sizes, surface area and binding affinities, or combinations thereof. To further enhance the efficacy of the general adsorbent, metal oxides or other metal-based complexes may be included in the general adsorbent section.

[0021] The selective adsorbent section 136 includes a selective adsorbent material 146 dispersed throughout a filter plug material 142, such as in a “dual-dalmatian” filter, known in the art. The selective adsorbent material 146 may be an ion-exchange resin, such as Duolite A7 (a phenol-formaldehyde resin matrix and is surface-functionalized with primary and secondary amino groups available from Rohm and Haas, 5000 Richmond Street, Philadelphia, Pa. 19137), or a material having similar functional groups and binding affinities.

[0022] When the cigarette is consumed, the tobacco smoke is puffed by the smoker through the filter 130. The smoke initially passes over the selective adsorbent section 136 where the targeted smoke constituents are adsorbed on the surface of the selective adsorbent material 146 and particulate matter in the smoke is retained by the filter plug material 142. The remaining smoke then passes over the general adsorbent section 134 where other constituents may be retained by the adsorbent material 144 and additional particulate matter is retained by the filter plug material 142. Finally, the remaining smoke then passes through the filter plug 132 where additional particulate matter can be removed. The filtered smoke is then delivered to the smoker.

[0023] In an alternative embodiment, such as shown in FIG. 3, a cigarette 210 has a multiple section filter 230 wherein the filter plug 132 is positioned at the mouth end 131, the general adsorbent section 134 is adjacent the tobacco-rod end 137, and the selective adsorbent section 136 is sandwiched between the filter plug 132 and the general adsorbent section 134. In this embodiment, during a normal puff, the smoke first passes through the general adsorbent section 134, then through the selective adsorbent section 136, and finally through the filter plug 132.

[0024] As shown in another embodiment in FIG. 4, in a multiple section filter 330 of a cigarette 310, the absorbents 144, 146 are packed within the filter plug material as thin layer sections of general absorbent 344 and selective absorbent 346. In this embodiment, the layer packed absorbents are exposed to less plasticizer than the tow-dispersed absorbents and retain more surface area for interacting with smoke constituents. Moreover, as shown in FIG. 7, a multi-section filter 630 for a cigarette 610 includes the general adsorbent 344 and the selective adsorbent 346 dispersed in separate sections within a single length of fibrous filter material 342.

[0025] An advantage of the embodiment 110 of FIG. 2 is that the smoke passes over the selective adsorbent material 146 before passing over the general adsorbent 144. This allows the selective adsorbent 146 to remove some specific smoke constituents before the general adsorbent 144 is exposed to the smoke, thereby allowing the general adsorbent 144 to be more effective in removing the remaining smoke constituents. Thus, there is a synergistic effect observed for the adsorbents in the cellulose acetate/general adsorbent/specific adsorbent orientation as compared to the cellulose acetate/specific adsorbent/general adsorbent orientation.

[0026] As shown in FIGS. 5 and 6, in a multiple section filter 430 and 530 of cigarettes 410 and 510, respectively, the filter plug 132 is disposed between the general adsorbent section 134 and the selective adsorbent section 136 in FIG. 5 and is adjacent one end of the tobacco rod 20 in FIG. 6. In FIG. 5 the selective adsorbent section 136 is at the mouth end of the filter 430 and in FIG. 6 the general adsorbent section 134 is at the mouth end of the filter 530. Moreover, as shown in FIG. 8, a multiple section filter 730 of a cigarette 710 includes only a general absorbent section 134 and a selective absorbent section 136.

[0027] The following examples are representative of the embodiments which can be prepared in accordance with the present invention and the smoke constituent removal performance of those embodiments. The embodiments presented are intended for example purposes only and are not intended to be limiting in scope.

[0028] Example 1: A cigarette 110 with a multiple section filter 130 is prepared as shown in FIG. 2 wherein a filter plug 132 is made of cellulose acetate tow and is about 7 mm in length, a general adsorbent section 134 consists of about 40 mg of activated coconut charcoal 144 dispersed throughout plasticizer-treated cellulose acetate tow 142 cut to deliver a section 134 about 10 mm in length, and a selective adsorbent section 136 consists of about 40 mg of Duolite A7 dispersed throughout plasticizer-treated cellulose acetate tow 142 cut to deliver a section 136 about 10 mm in length. The filter is attached to a tobacco rod having a length of about 56.5 mm and containing about 617 mg of a typical non-menthol cigarette blend wrapped in a 50 Coresta cigarette paper with about 1.8% citrate. The cigarette delivers about 10.3 mg tar per cigarette.

[0029] Example 2: A cigarette 210 with a multiple section filter 230 is prepared with the section orientations as shown in FIG. 3 wherein the filter plug 132, the general adsorbent section 134, and the selective adsorbent section 136 are essentially identical to the filter plug 132, the general adsorbent section 134, and the selective adsorbent section 136 of Example 1. The filter is attached to a tobacco rod having a length of about 56.5 mm and containing about 617 mg of a typical non-menthol cigarette blend wrapped in a 50 Coresta cigarette paper with about 1.8% citrate. The cigarette delivers about 10.0 mg tar per cigarette.

[0030] Example 3: Cigarettes are prepared as in Example 1 except that about 20 mg Duolite A7 is used in the selective adsorbent section 136 instead of 40 mg. The cigarette delivers about 10.2 mg tar per cigarette.

[0031] Example 4: Cigarettes are prepared as in Example 2 except that about 20 mg Duolite A7 is used in the selective adsorbent section 136 instead of 40 mg. The cigarette delivers about 10.9 mg tar per cigarette.

[0032] Example 5: Cigarettes are prepared as in Example 1 except that about 60 mg Duolite A7 is used in the selective adsorbent section 136 instead of 40 mg. The cigarette delivers about 10.0 mg tar per cigarette.

[0033] Example 6: Cigarettes are prepared as in Example 2 except that about 60 mg Duolite A7 is used in the selective adsorbent section 136 instead of 40 mg. The cigarette delivers about 10.3 mg tar per cigarette.

[0034] Example 7: Cigarettes are prepared as in Example 1 except that about 69 mg of a mineral-based charcoal made from semi-anthracite coal is used in the general adsorbent section 136 instead of 40 mg of activated coconut charcoal. The cigarette delivers about 10.1 mg tar per cigarette.

[0035] Example 8: Cigarettes are prepared as in Example 2 except that about 69 mg of a mineral-based charcoal made from semi-anthracite coal is used in the general adsorbent section 136 instead of 40 mg of activated coconut charcoal. The cigarette delivers about 10.2 mg tar per cigarette.

[0036] Example 9: Representative cigarettes of Examples 1-6 are smoked to a butt length of about 4 mm from the tipping using a Borgwalt RM-20 smoking machine. Following the procedures set forth by the FTC, smoke constituents exiting the filter end of each cigarette are passed through a Cambridge filter pad, the vapor phase is collected in a bag and analyzed by GC/MS. The data is normalized to about 10 mg tar per cigarette. Average Vapor Phase Yields (μg/cig) mg Duolite/cigarette 40 20 60 Cigarettes Prepared by Example: 1 2 3 4 5 6 Filter Segment Order CA/GA/SA CA/SA/GA CA/GA/SA CA/SA/GA CA/GA/SA CA/SA/GA Acetaldehyde 330.9 333.7 380.7 346.2 320.3 310.9 Isoprene 231.4 240.4 252.1 246.1 227.4 227.2 Acetone 144.1 163.5 156.0 160.5 148.0 151.4 Methanol 104.9 127.6 114.5 142.8 111.7 98.5 Acetonitrile 59.8 72.0 67.0 77.4 62.8 57.3 Acrolein 29.6 31.4 33.6 32.2 28.5 29.9 Methyl ethyl ketone 29.3 35.9 30.9 38.5 30.1 31.6 Formaldehyde 23.5 25.8 25.5 25.0 22.1 24.5 Propionaldehyde 25.7 27.4 29.3 28.5 25.3 25.0 1,3-Butadiene 25.5 25.9 27.5 25.5 25.8 25.0 Toluene 22.5 25.3 22.0 27.5 23.9 22.5 Benzene 20.6 23.6 21.6 24.1 21.1 21.4 Acrylonitrile 16.8 17.7 18.0 18.0 17.0 16.5 Furan 16.2 17.0 17.3 16.4 16.4 16.2 Hydrogen cyanide 15.1 16.4 20.7 19.6 13.6 14.8 Hydrogen sulfide 12.9 13.0 14.0 12.9 13.1 12.7 Propionitrile 12.9 15.0 13.5 15.9 13.6 12.8 2-Methylpropanal 6.4 6.7 7.0 7.0 6.6 6.4 Crotonaldehyde 5.1 5.9 5.5 6.3 5.3 5.0 Carbon disulfide 2.5 2.6 2.7 2.6 2.6 2.5 Styrene 2.0 1.8 2.2 1.9 2.1 1.7 Pyridine 1.9 1.9 1.9 1.8 1.9 1.8

[0037] Example 10: Representative cigarettes of Examples 7 and 8 are smoked to a butt length of about 4 mm from the tipping using a Borgwalt RM-20 smoking machine. Following the procedures set forth by the FTC, smoke constituents exiting the filter end of each cigarette are passed through a Cambridge filter pad, the vapor phase is collected in a bag and analyzed by GC/MS. The data is normalized to about 10 mg tar per cigarette. Average Vapor Phase Yields (μg/cig) mg Duolite/cigarette 40 Cigarettes Prepared by Example: 7 8 Filter Segment Order CA/GA/SA CA/SA/GA Acetaldehyde 343.4 364.2 Isoprene 225.0 268.9 Acetone 138.6 162.3 Methanol 95.1 134.7 Acetonitrile 61.4 84.6 Acrolein 9.8 35.3 Methyl ethyl ketone 28.3 39.8 Propionaldehyde 26.4 30.2 1,3-Butadiene 25.4 27.7 Toluene 18.7 24.2 Benzene 21.3 27.3 Acrylonitrile 7.5 9.0 Furan 17.0 18.4 Hydrogen cyanide 16.7 19.5 Hydrogen sulfide 14.7 14.1 Propionitrile 15.7 20.3 2-Methylpropanal 13.0 14.8 Crotonaldehyde 3.3 5.1 Carbon disulfide 2.8 2.8 Styrene 1.8 2.1 Pyridine 1.3 1.4

[0038] From a production perspective, there are some advantages to dispersing the selective adsorbent material 146 and the general adsorbent material 144 throughout the filter tow 142. Specifically, when the adsorbents 144, 146 are dispersed within the tow 142, the adsorbents are easier to handle than they are as loose particles. However, when the adsorbents 144, 146 are dispersed within the tow 142, there is a risk that any plasticizer which is used on the tow 142 will affect the surface of the adsorbents 144, 146, thereby reducing the adsorption capacity. Thus, as shown in FIG. 4, the adsorbents 144, 146 may be packed within the filter plug material 142 as thin layer sections of general adsorbent 344 and selective adsorbent 346. Because the layer packed adsorbents would not be exposed to the same level of plasticizer as the tow-dispersed adsorbents, the adsorbents would retain more available surface area for interacting with smoke constituents.

[0039] From a reading of the above, one with ordinary skill in the art should be able to devise variations to the inventive features. For example, the filter plug, the general adsorbent section, and the selective adsorbent section may vary in length and diameter, relative to any dimensions specified herein and relative to each other. Further, the various section dimensions may be optimized for a particular tobacco blend or for particular tobacco rod dimensions. These and other variations are believed to fall within the spirit and scope of the attached claims. 

What is claimed is:
 1. A multiple section cigarette filter comprising: (a) a selective adsorbent section comprising an ion-exchange resin having a phenol-formaldehyde resin matrix that is surface-functionalized with primary and secondary amine groups, said resin being dispersed throughout a fibrous material; and (b) a general adsorbent section comprising a general adsorbent material having a high surface area and being capable of adsorbing smoke constituents without a high degree of specificity, said selective adsorbent section and said general adsorbent section being co-axially aligned in tandem.
 2. The cigarette filter of claim 1 wherein said general adsorbent material is selected from the group consisting of activated charcoal, activated coconut carbon, activated coal-based carbon, zeolite, silica gel, meerschaum, aluminum oxide, a coal-based charcoal made from semi-anthracite coal, a carbonaceous resin derived from the pyrolysis of sulfonated styrene-divinylbenzene, or combinations thereof.
 3. The cigarette filter of claim 2 wherein said general adsorbent section further includes a metal oxide or other metal-based complex.
 4. The cigarette filter of claim 1 including a fibrous filter plug wherein said filter plug is made from cellulose, cellulose acetate tow, paper, cotton, polypropylene web, polypropylene tow, polyester web, polyester tow or a combination thereof, said fibrous filter plug being co-axially aligned in tandem with said selective adsorbent section and said general adsorbent section.
 5. The cigarette filter of claim 4 wherein said filter plug further includes a plasticizer, a liquid additive, a flavoring agent or a combination thereof.
 6. The cigarette filter of claim 4 wherein said general adsorbent section is positioned between said fibrous filter plug and said selective adsorbent section.
 7. The cigarette filter of claim 4 wherein said selective adsorbent section is positioned between said fibrous filter plug and said general adsorbent section.
 8. The cigarette filter of claim 4 wherein said filter plug is made from cellulose acetate tow, said selective adsorbent material is an ion-exchange resin having a phenol-formaldehyde resin matrix and is surface-functionalized with primary and secondary amine groups, and said general adsorbent section comprises activated coconut charcoal dispersed throughout plasticizer-treated cellulose acetate tow.
 9. The cigarette filter of claim 8 wherein said general adsorbent is positioned between said fibrous filter plug and said selective adsorbent section.
 10. The cigarette filter of claim 8 wherein said selective adsorbent section is positioned between said fibrous filter plug and said general adsorbent section.
 11. The cigarette filter of claim 4 wherein said filter plug is made from cellulose acetate tow, said selective adsorbent material is an ion-exchange resin having a phenol-formaldehyde resin matrix and is surface-functionalized with primary and secondary amine groups, and said general adsorbent section comprises mineral-based charcoal made from semi-anthracite coal dispersed throughout plasticizer-treated cellulose acetate tow.
 12. The cigarette filter of claim 11 wherein said general adsorbent is positioned between said fibrous filter plug and said selective adsorbent section.
 13. The cigarette filter of claim 11 wherein said selective adsorbent section is positioned between said fibrous filter plug and said general adsorbent section.
 14. The cigarette filter of claim 4, said fibrous filter plug being positioned between said selective adsorbent section and said general adsorbent section.
 15. The cigarette filter of claim 1, said selective absorbent material having a surface area greater than about 35 m²/g.
 16. The cigarette filter of claim 1 including a plug wrap circumscribing said general adsorbent section and said selective adsorbent section.
 17. A multiple section cigarette filter comprising: (a) a fibrous filter plug; (b) a selective adsorbent section comprising an ion-exchange resin having a phenol-formaldehyde resin matrix that is surface-functionalized with primary and secondary amine groups, said resin being dispersed throughout a fibrous material; and (c) a general adsorbent section comprising a general adsorbent material selected from the group consisting of activated charcoal, activated coconut carbon, activated coal-based carbon, zeolite, silica gel, meerschaum, aluminum oxide, a coal-based charcoal made from semi-anthracite coal, a carbonaceous resin derived from the pyrolysis of sulfonated styrene-divinylbenzene, or combinations thereof, said fibrous filter plug, said selective adsorbent section, and said general adsorbent section being co-axially aligned in tandem.
 18. The cigarette filter of claim 17 wherein said general adsorbent section further includes an additive selected from a metal oxide or another metal-based complex.
 19. The cigarette filter of claim 17 wherein said general adsorbent material is dispersed throughout a fibrous material.
 20. The cigarette filter of claim 17 wherein said general adsorbent section comprises a close-packed bed of said general adsorbent material.
 21. The cigarette filter of claim 17 wherein said filter plug is made from cellulose, cellulose acetate tow, paper, cotton, polypropylene web, polypropylene tow, polyester web, polyester tow or a combination thereof.
 22. The cigarette filter of claim 17 wherein said filter plug further includes a plasticizer, a liquid additive, a flavoring agent or a combination thereof.
 23. The cigarette filter of claim 17 wherein said general adsorbent section is positioned between said fibrous filter plug and said selective adsorbent section.
 24. The cigarette filter of claim 17 wherein said selective adsorbent section is positioned between said fibrous filter plug and said general adsorbent section.
 25. The cigarette filter of claim 17 wherein said filter plug is made from cellulose acetate tow, said selective adsorbent material is an ion-exchange resin having a phenol-formaldehyde resin matrix and is surface-functionalized with primary and secondary amine groups, and said general adsorbent section comprises activated coconut charcoal dispersed throughout plasticizer-treated cellulose acetate tow.
 26. The cigarette filter of claim 17 wherein said filter plug is made from cellulose acetate tow, said selective adsorbent material is an ion-exchange resin having a phenol-formaldehyde resin matrix and is surface-functionalized with primary and secondary amine groups, and said general adsorbent section comprises bituminous-based charcoal made from semi-anthracite coal dispersed throughout plasticizer-treated cellulose acetate tow.
 27. The cigarette filter of claim 17, said selective absorbent material having a surface area greater than 35 m²/g.
 28. The cigarette filter of claim 17, said fibrous filter plug being positioned between said selective adsorbent section and said general adsorbent section.
 29. The cigarette filter of claim 21 wherein said general adsorbent section is positioned between said fibrous filter plug and said selective adsorbent section.
 30. The cigarette filter of claim 21 wherein said selective adsorbent section is positioned between said fibrous filter plug and said general adsorbent section.
 31. The cigarette filter of claim 21, said selective absorbent material having a surface area greater than 35 m²/g.
 32. The cigarette filter of claim 21, said fibrous filter plug being positioned between said selective adsorbent section and said general adsorbent section.
 33. The cigarette filter of claim 21, said filter plug, said selective adsorbent section, and said general adsorbent section being circumscribed with a plug wrap. 